1. Field of the Invention
The present invention relates to a storage system configured by connecting a plurality of storage nodes each of which having a storing device via a network.
2. Description of the Related Art
With the increase of using digital data and the increase of a demand for storing large amount of archived data, a storage device that performs operations concurrently for a plurality of disk devices has become popular (see, for example, Japanese Patent Application Laid-Open No. 2000-330732). The storage device includes a plurality of storage nodes containing a controller and a plurality of magnetic disk devices controlled by the controller, connected via a network, thereby realizing a higher capacity of data storage. On the other hand, because the storage device uses a lot of magnetic disk devices, there has been a problem that power consumption becomes higher. Generally, the power consumption has been reduced by changing operating state of the magnetic disk devices to be in standby state when the magnetic disk devices do not receive an access request such as a read request or a write request for a certain time period.
However, with the conventional technology, it is difficult to simultaneously realize maximizing access efficiency and reducing power consumption. Namely, when a higher priority is put on maximizing access efficiency, the magnetic disk devices in the storage device cannot be set in the standby state (e.g., a motor needs to be rotating even if a head is unloaded so as to keep a condition for receiving an access). Therefore it is difficult to simultaneously realize maximizing access efficiency and reducing power consumption.